1. Field of the Invention
The present invention relates to torque limiting or torque release clutches which provide for a torque tending to reset the clutch to an indexed position after the breakaway torque has been exceeded.
2. Prior Art
In the prior art various types of overload torque clutches have been advanced, and several of these operate on a principle wherein the drive position of the clutch is preset at an indexed position between the drive and driven portions. Such a device is shown in U.S. Pat. No. 3,643,770. The clutch in that patent is a dog type overload torque clutch with fingers that release under excessive load. The drive and driven parts then rotate to a position wherein the stops again engage.
Many types of magnetic clutches have also been advanced wherein magnets on the drive and driven members are annular and face each other, and limit the torque transmitted to the magnetic force. However, such clutches do not have a positive indexed position between the drive and driven members, and thus operate much like ordinary friction clutches. Typical showings of such magnetic clutches include U.S. Pat. Nos. 3,837,232, and 3,446,321. Other patents which illustrate single revolution type clutches as well as torque limiting clutches include U.S. Pat. Nos. 2,711,237 and 3,712,433.
A power wrench with magnetic sleeves for variable torque output is shown in U.S. Pat. No. 3,974,884, but again this type of device permits rotation of the input shaft relative to the output under a continuous magnetic force.